1. Field of the Invention
The present invention relates to a lens barrel which is arranged to restrain an image shake by detecting a vibration occurring in an optical apparatus such as a camera and moving correcting optical means in a direction perpendicular to the optical axis of the lens barrel by using the detected vibration as information for preventing an image shake, as well as to an optical apparatus having such lens barrel.
2. Description of Related Art
All the operations of current cameras that are important for photography, such as exposure decision and focusing, are automated, and even persons who are unfamiliar with camera operation rarely fail in photography. In addition, a system for correcting a vibration applied to a camera and preventing an image shake has recently been developed, and is proposed in, for example, Japanese Laid-Open Patent Application No. Hei 3-188430.
A camera system for preventing an image shake will be briefly described below.
Vibrations which are applied to cameras during photography normally have a frequency of 1 Hz to 12 Hz, and a basic concept for enabling a user to take a photograph free of an image shake with a camera even if such a vibration is applied thereto at the time of shutter release is to detect the vibration of the camera and displace the aforesaid correcting optical means according to the detected value.
Accordingly, in order to enable the user to take a photograph free of an image shake even if a vibration is applied to the camera, first, it is necessary to accurately detect the vibration of the camera, and secondly, it is necessary to correct a change based on the vibration in the photographing optical axis of the camera.
Theoretically, the detection of such vibration can be realized by incorporating vibration detecting means for detecting angular acceleration, angular speed, angular displacement and the like in a camera or a lens. An image shake can be restrained by driving and displacing correcting optical means for decentering the photographing optical axis on the basis of the detected information.
An image stabilizing system using such vibration Ad detecting means will be briefly described with reference to FIG. 8.
FIG. 8 schematically shows an example of a system for restraining an image shake derived from a vertical vibration p and a horizontal vibration y of a camera. The shown example includes a lens barrel 1, vibration detecting means 2p for detecting the vertical vibration p, and vibration detecting means 2y for detecting the horizontal vibration y. Reference numerals 3p and 3y denote the vibration detecting direction of the vibration detecting means 2p and the vibration detecting direction of the vibration detecting means 2y, respectively. The shown example also includes correcting optical means 4 which has coils 5p and 5y for giving thrust to the correcting optical means 4, and detecting elements 6p and 6y for detecting the position of the correcting optical means 4. The correcting optical means 4 is provided with a position control loop, and is driven by using the outputs of the vibration detecting means 2p and 2y as target values, to ensure stabilization of an image in an image plane 7.
As described above, as the number of functions of the apparatus itself is increased, more various elements such as vibration detecting means and driving means for driving the correcting optical means need to be incorporated into the apparatus. Accordingly, it is necessary to design the lens barrel so that a dead space therein can be efficiently used.
In the conventional lens barrel, since the vibration detecting means are provided in the vicinity of the mount of the lens barrel, the vibration detecting means need to be incorporated in a shield component which completely cover them, in order to reduce the disturbance of the vibration detecting means, such as the noise of a mirror-up operation of a camera.
However, if the vibration detecting means are disposed in the vicinity of the mount, as in the conventional example, an increase in the entire optical length of an optical system is involved.
In addition, the vibration detecting means need to have a shield component for preventing the disturbance, and needs a larger number of components and has the problem of inferior easiness of assembly.